The United Church of Christ became the first mainline Christian denomination to endorse gay marriage Monday when its 25th biennial General Synod decisively approved an "equal marriage rights for all" resolution.

The vote set off a celebration in the Georgia World Congress Center. Gay couples hugged one another. Some wiped away tears. A group of UCC delegates joined hands afterward and sang, "Amen." But other delegates rushed from the hall warning of schism within the 1.6 million member denomination.

The Rev. John H. Thomas, the president of the UCC, drew a link between the vote and the historical significance of another event on Monday.

"On this July Fourth, the General Synod of the United Church of Christ has acted courageously to declare freedom," said Thomas, who was re-elected to another term. He announced June 28 that he supported the resolution.

The vote affirms equal marriage rights for couples regardless of gender and says that the government should not interfere with same-sex couples who want to marry. It calls on denomination officers to press local, state and national legislators to support equal marriage rights.

Many mainline denominations, including the Presbyterian Church USA, the United Methodist Church and the Episcopal Church, also are wrestling with the issue.

Some members fear the issue could tear denominations apart much like slavery did in the 19th century.

Spain joined Belgium and the Netherlands last week in legalizing gay marriage. In Canada, the House of Commons has approved gay marriage and the Senate is expected to follow suit this month.

The Rev. Andrew Young, former mayor of Atlanta and a member of the United Church of Christ, was honored by the denomination at the convention. He had endorsed the resolution, and in remarks after receiving his award he praised the UCC's activist tradition. The UCC, which helped inspire the Boston Tea Party, says it was the first denomination to ordain a black pastor (1785) and a woman (1853).

"What seemed controversial back then seems so automatic today," Young said before the vote. "We wonder why it was a struggle at all. There's no education without controversy and there's no resurrection without crucifixion."

Opponents told the synod that the resolution ignores Jesus' declaration that marriage is between a man and woman.

Others said the denomination would lose members and financial support.

One group, Biblical Witness Fellowship, fought unsuccessfully for the resolutions' defeat. It's executive director, the Rev. David Runnion-Bareford, dismissed the UCC's slogan — "God is Still Speaking" — which some supporters of the resolution used to justify their position.

"God is still speaking; but they're speaking for God," Runnion-Bareford said. "They're going to redefine marriage speaking in the name of God. It's quite arrogant. Who dropped dead and left them in charge?"

Members from the Southern California conference that offered the resolution argued that marriage was an evolving institution and pointed to Biblical passages where polygamy was accepted, women were property and interracial marriages were taboo.

Lisa Stedman, a UCC delegate, walked before a microphone with her partner, Johanna, and said they didn't want to be partners. They wanted to marry.

"Separate but equal has never worked, and equal but different has never been truly equal," Stedman said.

The Rev. Timothy Downs, head of the Southeast region, thinks some Atlanta congregations will embrace the resolution and others will struggle with it. Victory for the World United Church of Christ in Stone Mountain is the denomination's second-largest congregation in the country.

Downs said membership in the Southeast Conference has doubled to 12,000 since 1996. Four of the nine UCC churches in metro Atlanta area officially welcome gays and lesbians.

"Jesus Christ came first for the locked-out and those left behind," Downs said. "The overarching commandment from Jesus Christ is that we're to love God and our neighbors as ourselves. This decision is congruent with that commandment."

Thomas said he wanted the UCC to understand in the tense days ahead that "unity does not mean uniformity."

"My hope is that we won't run from one another," he said. "When we run from one another, we run from Christ."